DE19937185A1 - Object detection apparatus for vehicle does not add reflected signals together if affected intense reflections from roadside reflector - Google Patents

Abstract

The apparatus detects objects such as a vehicle in front (T1) or a roadside reflector (R1). In the event that the vehicle in front (T1) and a roadside reflector (R1) lie side by side, if the received signals of the reflected waves from the objects are added for each beam, then strong reflections from the reflector (R1), cause the vehicle in front (T1) and the reflector to merged together. Therefore, in the region affected by the reflected wave from the reflector (R1), the received reflected wave signals are not added together for each beam and only the reflector (R1) is detected. In the regions not affected by the reflected wave from the reflector, the addition is performed and the vehicle in front is detected. Thus, the separation between the reflector and the vehicle in front can be detected. An object detection method is also included.

Description

The present invention relates to an object detection device for detecting an object by emitting an electromagnetic Wave, in particular comprising laser radiation or Millimeter wave radiation, to the object and receiving one of them reflected wave.

The applicant has developed an object detection device (see Japanese Patent Application No. 10-200035 and the corresponding German Patent Application P 199 32 975) which is designed to measure distances to targets T ₁ , T ₂ ,. . . (ie vehicles traveling in front of an associated vehicle) and their lateral (lateral) positions by vertically and laterally scanning with an electromagnetic wave emitted forward by a "radar system" attached to a front portion of a vehicle V, and by receiving a wave reflected by the targets T ₁ , T ₂ . This device is included in the arrangement of FIG. 6, which shows an embodiment of the invention. In this object detection device, the space in which the detection of the targets T ₁ , T _2,. . . is to be performed, divided into a plurality of detection areas K1 to K15, which have a width substantially equal to the lateral width of the vehicle V. Each of the detection areas K1 to K15 is divided by distance addresses [1] to [200] into mesh-shaped areas (measuring areas) as a function of the distance to the vehicle V, so that the distances to the targets T ₁ , T ₂ ,. . . and whose lateral positions are detected based on a value resulting from the addition of signals indicating reception levels of the reflected waves in the measurement areas.

In the above object detection device, the detected lateral widths of the targets T ₁ , T ₂ ,. . . equal to the actual lateral widths of the targets T ₁ , T _2,. . ., provided there are no reflectors R ₂ , R ₂ on the rear surfaces of the targets T ₁ , T _2,. . . are attached. However, if highly reflective reflectors R ₂ , R ₂ on the rear surfaces of the targets T ₁ , T _2,. . . are attached, the signals indicating the reception levels of the reflected waves are amplified in an area in which the reflectors R ₂ , R _{2 are} contained, and also signals indicating the reception levels of the reflected waves in an area are amplified the reflectors R ₂ , R ₂ indicate, reinforced. Therefore, the lateral widths of the targets T ₁ , T _2,. . . as values greater than the actual lateral widths of the targets T ₁ , T _2,. . . he can be caught.

If a plurality of targets T ₁ , T _2,. . ., Which have highly reflective reflectors R ₂ , R ₂ , occur laterally adjacent to one another at the same distance, or if highly reflective reflectors R _{1 are} attached to a road and the reflectors R ₁ and the targets T ₁ , T _2,. . . another occur laterally adjacent at the same distance, there is a possibility that the targets T ₁ , T _2,. . . "merge", ie can no longer be distinguished and are recorded as a goal, or that the goals T ₁ , T ₂ ,. . . and the reflectors R ₁ "merge" on the road, that is to say they are detected as a target T ₁ , T ₂ with a large lateral width.

Accordingly, it is an object of the present invention to provide a To provide an object detection device in which a plurality of Objects that appear adjacent to each other at the same distance can be distinguished from each other. So it should be prevented that the goals are mistaken as a single object in the sense of a "Fusion" can be detected, which has a large lateral width.

To solve the above task, a Object detection device for detecting an object in a  Object detection area by emitting an electromagnetic wave and receiving a reflected wave resulting from a reflection of the electromagnetic wave resulting from the object provided. The The device comprises a transmitting and receiving means for transmitting the electromagnetic wave and receiving the reflected wave for everyone a plurality of small areas into which the object detection area was divided, a first storage means for storing signals Display the reception level of waves reflected from the small areas, in accordance with the time delay from transmission to Receiving the waves, a second storage means for storing Signals that receive levels from across a plurality of coverage areas Show reflected waves in the form of in accordance with the Time delay from sending to receiving the waves signals added together which indicate the reception level (Received signals), the detection ranges being defined by Group adjacent to the plurality of small areas so that they have a predetermined page width, and an object detection means to measure a distance to the object based on the result a comparison of an output from the first storage means with one Output from the second storage means.

According to the above configuration, a first storage means is provided for Saving the signals, the reception level in the small areas display, with the signals not being added to distance to deliver an object that has a high reflectivity for the has electromagnetic wave. Furthermore, a second storage means provided for storing the signals that receive levels in the small Display areas, these signals in a form corresponding to a The signals are added together in the detection area units, to provide distance to an object that is a bad one Has reflectivity for the electromagnetic wave. The Output of the first storage medium and the output of the second  Storage means are compared with each other, whereby the distance to the Object (the object distance) based on the result of the comparison is detected. If a plurality of objects as a single object could be mistaken as a result of being together "merge", due to the issue of the second Storage means the error detection can be prevented by the "Merging" through the output from the first storage means will be "redressed". This allows the majority of objects be reliably recorded, and that differentiation between the individual Objects.

In the disclosed embodiments, the predetermined lateral width is set to 1.6 m. However, this value is a question of design, which can be changed according to the size of an object to be detected. According to a first embodiment, a beam transmission section ( 1 ), a transmission beam scanning section ( 2 ), a beam reception section ( 3 ) and a reception beam scanning section ( 4 ) form a transmission and reception means, and in a third embodiment the beam transmission section ( 1 ), the transmission beam scanning section ( 2 ), the beam reception section ( 3 ) and a transmission and reception beam scanning section ( 4 ') a transmission and reception means. The scanning sections ( 2 , 4 , 4 ') can each also be referred to as a scanning or search section.

It is proposed that the second storage means be in a lateral position of the object (an object page position) based on a lateral Position of the detection area in which the object was detected.

With this interpretation, the lateral position of each of the first Detection areas determined according to the accumulation of small areas and the lateral position of the object can therefore be determined based on the  lateral position of the detection area in which the object was detected be recorded.

It is suggested that the majority of coverage areas be different are defined mutually overlapping, namely by half each other overlapping their lateral width.

With this design, the following is achieved: As the detection areas are defined to overlap each other by half the lateral width, Even if an object emerges in such a way that it can be divided into two neighboring page positions "occurs", the object in both Reliable coverage by covering by both Detection areas are recorded.

It is proposed that the second storage means extract values and outputs that exceed a threshold resulting from the addition of a Plurality of signals indicating reception level in accordance with the time delay between sending out and receiving the electromagnetic wave results.

With this interpretation, since one of the addition of a plurality of received signals in accordance with the time delay between sending and receiving the electromagnetic wave result, is extracted, namely a threshold exceeding value, reliably ensured that only one object through the extraction is detected, which is a sufficiently large one Receiving level of the reflected wave signal provides.

It is also proposed that the transmission and reception means the emits electromagnetic wave sequentially in the lateral direction, and that the first storage means is used to determine the lateral position of the object (the  Object page position) based on the timing of sending the to capture electromagnetic wave to each of the small areas.

With this design, since the transmission and reception means the electromagnetic wave sequentially with respect to the lateral direction emits the lateral position of the through the electromagnetic wave detected object based on the timing of sending out the electromagnetic wave detected by the transmitting and receiving means become.

It is also proposed that the object detection device on a Vehicle is attached to capture objects in front of the vehicle occur in the direction of movement of the vehicle, the lateral Width of the detection area based on the lateral width of the Vehicle or the width of a lane of the road is set.

With this design, because the lateral width of the detection area based on the lateral width of the vehicle or the lane is / will be a detection area of a reasonable size in Depends on the size of a vehicle driving in front of the vehicle (referring to the vehicle in front or in front) is taken), whereby the preceding vehicle can be reliably detected.

It is also proposed that the lateral width of the detection area substantially equal to the lateral width of the vehicle or the lane is / will be set.

With this design, the vehicle in front can move due to the Coverage reliably covered completely by the detection area because the lateral width of the detection area is essentially  is set equal to the lateral width of the vehicle or the lane.

It is further proposed that the object detection means the distance and the lateral position of the object, i.e. the object distance and the Object page position, (1.) detected based on data that remains after deleting the data for the object distances and for the Object page positions based on those in the first storage means stored data from the data for the object distances and the Object page positions based on those in the second storage means stored data, as well as (2.) on the basis of the in the first storage means stored data.

With this interpretation, a section in which the data for the Distances to and the lateral positions of the object based on the im first storage means stored data and the data for the distances to and the lateral positions of the object based on that in the second Storage means stored data, overlap each other, the data deleted from the second storage means and the data from the first Storage media used. Therefore, if a plurality of objects be misjudged as a single object due to "merging" could, based on the data from the second storage means, as itself signals resulting from the addition of the reception level signals Data has been saved that can be prevented by primarily the data from the first storage means that the the signals indicating the reception level without adding the signals saves. The majority of objects can thus be reliably detected differentiating the individual objects.

It is also proposed that the object detection device be a third Storage means includes for storing data for object distances and Object page positions (i.e. data for the distance to the object or the  Distances to the objects as well as the lateral position of the object or the lateral positions of the objects) based on that in the first Storage means stored data, and a fourth storage means for Store object distances and object page positions based on of the data recorded in the second storage means, the Object detection means the respective object distance and the respective Object page position captured (1.) based on data that remains after deleting the data for the object distances and object page positions, which are stored in the third storage means, from the data for the Object distances and the object page positions that are in the fourth Storage means are stored, as well as (2.) on the basis of the third Storage means stored data.

With this interpretation, a section in which the data for the Object distances and the object page positions, which in the third storage means are stored on the basis of those stored in the first storage means Data, and the data for the object distances and the Object page positions stored in the fourth storage means Basis of the data stored in the second storage means itself mutually overlap, the data deleted from the fourth storage means and uses the data from the third storage means. When a Plurality of objects as a single object as a result of one "Merging" could be mistaken based on that in the fourth Storage means stored data resulting from the addition of the resulting data received signals received, can therefore the error detection can be prevented by using the Data from the third storage means which indicates the reception levels Stores signals without adding them so that the plurality of Objects can be reliably detected by differentiating the objects.

It is also proposed that the object detection device be a third Storage means for storing object distances and  Object page positions based on those in the first storage means stored data and a fourth storage means for storing Data for object distances and object page positions based on the in data stored in the second storage means, the second Storage means stores data after deletion from the third Data stored in the storage means corresponds to data from the data stored in the first storage means, the Object detection means object distances and object side positions (1.) Basis of the data for the object distances and object page positions that are stored in the fourth storage means, and (2.) on the basis of the in third storage means recorded data.

With this design, data for the Object distances and the object page positions based on the first Storage means stored data is saved, the data after Deletion of the data stored in the third storage means corresponding data from those stored in the first storage means Data remain stored in the second storage means and the Data for the object distances and the object page positions in the fourth Storage means based on those stored in the second storage means Data saved. Therefore it is possible to eliminate a section in which the data for the object distances and the object side positions, the are stored in the third storage means, and the data for the Object distances and the object page positions that are in the fourth Object storage means are stored, overlap each other. It can therefore, prevent a plurality of objects from being a single one Object is mistaken as a result of "merging" in the data from the fourth storage means, the signals added together, the View, contain, and store receive levels, causing the majority of Objects that distinguish them from each other can be reliably detected can.  

The invention further relates to an object detection method for detection of an object in an object detection area by sending one electromagnetic wave and receiving one from the reflection of the electromagnetic wave reflected by the object resulting Wave, comprising: emitting the electromagnetic wave and Receiving the reflected wave for each of a plurality of small ones Areas into which the object detection area is / is divided, Providing first data, the reception level from the small Reflected waves represent areas in accordance with the Time delay from transmission to reception of waves, Providing second data, the reception level of in a plurality waves reflected from detection areas represent in shape of received signals added together in accordance with the Time delay from sending to receiving the waves, where the detection areas are defined by grouping adjacent ones Plurality of small areas such that they have a predetermined Have page width, and detecting a distance to the object Basis of a result of the comparison of the first with the second Data.

The above and other objects, features and advantages of the invention are from the following description of preferred embodiments in connection with the accompanying drawings.

Fig. 1 to 12 show a first and a second embodiment of the present invention, wherein

Fig. 1 is a block diagram of an object detection apparatus according to the first embodiment of the present invention;

Fig. 2 is a perspective view of the object detection device;

Fig. 3 is an illustration for explaining a scanning method (scanning method, scanning or search method);

Fig. 4 is a diagram for explaining a scanning method (scanning method, scanning or search method);

. 5 is a block diagram of an essential part of Fig object detection apparatus,

Fig. 6 is a diagram for explaining the base areas and detection areas;

Fig. 7 is an enlarged diagram of a portion 7 shown in Fig. 6;

Fig. 8 is a diagram for explaining the operation;

Fig. 9 is a diagram for explaining the operation;

Fig. 10 is a first part of a flow chart for explaining the operation;

Fig. 11 is a second part of the flow chart for explaining the operation;

Fig. 12 is a third part of the flow chart for explaining the operation;

Fig. 13 to 16 show a third embodiment of the present invention, wherein

Fig. 13 is a block diagram of an object detection device;

Fig. 14 is a perspective view of the object detection device;

Fig. 15 is an illustration for explaining a scanning method (scanning method, scanning or search method);

Fig. 16 is a diagram for explaining a scanning method (scanning method, scanning or search method is).

First and second embodiments of the present invention will now be described with reference to FIGS. 1 to 12.

Figs. 1 and 2 show an object detecting device for detecting the distance between a vehicle V and a target T, for example, another traveling ahead of the vehicle V vehicle (reference is made to the as preceding vehicle or preceding vehicle) as well as to detect Direction to the vehicle in front. The object detection device comprises a beam transmission section 1 , a transmission beam scanning section 2 , a beam reception section 3 , a reception beam scanning section 4 and a distance measuring section 5 . The "scanning sections" 2 and 4 can each also be referred to as a scanning or scanning section 2 or 4 (or - in any case in the exemplary embodiment described here - also as a sweeping or back-and-forth pivoting section 2 or 4 ) become.

The beam transmission section 1 comprises a laser diode 11 which is integrally provided with a beam transmission lens, and a laser diode driver circuit 12 for driving (driving) the laser diode 11 . The transmission beam scanning section 2 comprises a beam transmission mirror 13 for reflecting the laser output of the laser diode 11 , a motor 15 for rotating the beam transmission mirror 13 back and forth about a vertical axis 14 and a motor control circuit 16 for controlling the drive of the motor 15 . The laser beam output from the beam transmitter mirror 13 has a vertically elongated beam profile as a result of a lateral width restriction. The target T is laterally scanned (scanned, scanned) by this laser beam with a period of 1400 msec.

The laser receiving section 3 includes a beam receiving lens 17 , a photodiode 18 for receiving the reflected beam focused by the beam receiving lens 17 to convert the beam into an electrical signal, and a receiving beam amplifying circuit 19 for amplifying the signal output from the photodiode 18 . The received beam scanning section 4 includes a beam receiving mirror 20 for reflecting the wave reflected from the target so as to couple it into the photodiode 18 , a motor 22 for rotating the beam receiving mirror 20 back and forth about a transverse axis (side axis) 21, and a motor drive circuit 23 for controlling the drive of the motor 22 . A beam reception area scanned vertically by the beam reception mirror 20 with a period of 10 msec has a laterally elongated profile as a result of a restriction in vertical width.

The distance measuring section 5 includes a control circuit 24 for controlling the laser diode driver circuit 22 and the motor control circuits 16 and 23 , a communication circuit 26 for carrying out communication between an electronic control unit (ECU) 25 for controlling a driving control system (cruise control system) and an automatic braking device, a memory circuit 27 for storing a signal (laser beam reception level signal) indicative of laser beam reception level, and a central processor unit (CPU) 28 as an object detection means for calculating a distance from the vehicle to the target T based on the Time between sending and receiving the beam.

As shown in FIGS. 3 and 4, the target T is a period of 200 msec by the vertically elongated laser beam from the Objekterfas sungsvorrichtung side (lateral, in the transverse direction) scanned (scanned is searched), and the laterally elongated beam receiving area for the Object detection device is scanned vertically with a period of 2.5 msec. A portion where the laser beam and the beam receiving area intersect is a single small area. The entire area in which the scanning (scanning, searching or panning back and forth) is carried out comprises a collection or grouping of a total of 400 small or smaller areas, which are divided by dividing the total area into 5 sections in the vertical direction and dividing the total area in 80 sections are created in the lateral direction (transverse direction). The 400 small areas are scanned in a zigzag pattern within 200 msec.

As shown in FIG. 6, the detection of the targets T ₁ , T ₂ and T _{3 is carried out} in a range from the vehicle V to a point 100 m in front of the vehicle V. The area from the vehicle V to the point 100 m in front of the vehicle V is divided into sixteen basic areas F1 to F16, which have a width of 0.8 m, by means of a plurality of parallel lines which are drawn parallel to a vehicle body axis CL of the vehicle V . Seen from the vehicle V, the base areas from the first base area F1 to the 16th base area F16 are arranged laterally symmetrically from left to right. The boundary between the eighth base area F8 and the ninth base area F9 coincides with the vehicle body axis CL of the vehicle V. As can be seen in FIG. 6, the vehicle body axis CL is a vehicle longitudinal axis.

An area created by adding adjacent base areas is as Detection area defined: one by adding the first and second Base area F1 and F2 area created to each other is the first Detection range K1 defined, one by adding the second and third Base area F2 and F3 area created to each other is second Detection range K2 defined, and one by adding the third and fourth base area F3 and F4 area created to each other is third Detection area K3 defined. By combining the first to 16th Base areas F1 to F16 in the above manner are the first to 15. Detection area K1 to K15 defined in a divided manner sequentially from left to right, with the detection areas each overlap by 0.8 m. The width of each of the detection areas K1 to K15 is 1.6 m. This value is chosen to be approximately the same is the side width of a typical typical vehicle V. The width of each the detection ranges K1 to K15 can be slightly larger than  1.6 m enlarged and on the order of the page width one usual typical street lane.

As can be seen by referring to FIG. 6 in combination with FIG. 7, the first to 16th base regions F1 to F16 are defined in the form of a band with a width of 0.8 m and in regions with a dimension of 0.5 m divided as a function of the distance from the vehicle V, a distance address being assigned to each area corresponding to a distance of 0.5 m. For example, the distance address [1] corresponds to a distance of 0.5 m, the distance address [2] corresponds to a distance of 1.0 m, the distance address [100] corresponds to a distance of 50.0 m and corresponds to the distance address [200] a distance of 100.0 m. Therefore, the total area in which the detection of the targets T ₁ to T _{3 is} carried out (a triangular area in Fig. 6) is divided into fine mesh-shaped areas (measuring areas by the base areas F1 to F16 and the distance addresses [1] to [200] ) divided.

The laser beam emitted by the vehicle V expands radially. Areas for which there is the possibility that the targets T ₁ , T ₂ and T _{3 could be} detected in the first base area F1 located at the leftmost position (as seen from the vehicle V) are areas which correspond to the distance addresses [195] to [ 200]. Areas for which there is a possibility that the targets T ₁ , T ₂ and T _{3 could be} detected in the second base area F2, which lies laterally inward adjacent to the first base area, are areas which correspond to the distance addresses [190] to [200] correspond. The range of distance addresses for which there is the possibility of acquiring the targets T ₁ to T ₃ thus increases when the respective target is closer to the vehicle body axis CL of the vehicle V. In the adjoining eighth and ninth base areas F8 and F9 on opposite sides of the vehicle body axis CL of the vehicle V, there is a possibility that the targets T ₁ , T ₂ and T _{3 could be} detected at all distance addresses [1] to [200].

In an area of the distance address [200], 100 m away from Vehicle V are five to the side in each of the base areas F1 to F16 contain juxtaposed rays. The density of each in the Base areas F1 through F16 contained rays increase when the Distance address decreases, so the distance to vehicle V is smaller. For example, in a range of the distance address [100] is in the distance of 50 m from vehicle V, in a certain basic range the density of the contained rays twice the density in a range of Distance address [200], 100 m from vehicle V.

The arrangement / layout of an essential part of the object detection device will now be explained with reference to FIG. 5.

The memory circuit 27 connected to the beam receiving section 3 includes an AD converter 29 for performing analog-to-digital conversion of a signal indicative of the reception level of a reflected wave received by the beam receiving section 3 , a latch circuit 30 for temporarily holding the AD converted , the signal indicating the reception level and a base clock circuit 31 for outputting a pulse signal of a given period to the latch circuit 30 .

A beam memory 32 A is connected as a first memory means to the latch circuit 30 and contains 200 memory areas which correspond to the distance addresses [1] to [200]. Therefore, when the reflected wave generated by the reflection of the laser beam emitted to each of the smaller areas from the target is received, the signal indicating the reception level is stored in the memory area corresponding to the distance to the target.

An adding memory 32 B is connected to the beam memory 32 A as a second storage means by an adding area selector 34 and contains storage areas for storing a large number of data points [D195, F1], [D196, F1], [D127, F1]. . . [D199, F16] and [D200, F16], which are recognized by the base areas F1 to F16 and the distance addresses [1] to [200]. The first half of the data stored in each of the memory areas corresponds to the distance addresses, and the second half corresponds to the base areas Nos. F1 to F16.

As can be seen even from FIG. 7, the first six of the memory areas in the adding memory 32 B correspond to the six measurement areas in the first base area F1, which are at a left end, and the next eleven of the memory areas correspond to the eleven measurement areas in the second base area F2 . The adder range selector 34 , which is connected to the control circuit 24 , stores the AD-converted signals which indicate the reception level in a memory area of the adder memory 32 B which corresponds to the distance to and the direction to the target which has reflected the laser beam The basis of the direction of transmission of the laser beam and the time delay from transmission to reception of the laser beam were determined. The distance of 0.5 m, which corresponds to a distance (interval) for recognizing the distance of the target, corresponds to the period of the pulse signal output by the base clock circuit 31 .

The central processor unit 28 of the object detection device of the present embodiment calculates the distance and lateral position of the target based on data stored in the beam memory 32 A and enables the results of the calculation to be stored in a beam target memory 33 A. The beam target memory 33 A constituting the first storage means or a third storage means of the present embodiment contains storage areas for storing data points [BT0], [BT1],. . . for distances to and side positions from a plurality of targets. When a plurality of targets have been detected, the distances (distances) and lateral positions of the targets are stored sequentially. The central processing unit 28 also calculates distances to and side positions allows the objectives to be added based on the memory 32 B stored data, and that the results of the calculation are stored in a destination memory 33 B. The target memory 33 B constituting the second storage means or a fourth storage means of the present embodiment contains storage areas for storing data points [T0], [T1],. . . for distances to and side positions from a plurality of targets. When a plurality of targets have been detected, the distances and lateral positions of the targets are stored sequentially.

The central processor unit 28 determines which of the data stored in the beam target memory 33 A and the data stored in the target memory 33 B are used and deletes the unused data. The function of the central processor unit 28 is described in detail below.

A procedure for calculating the distance to the lateral position of the target on the basis of the signal indicating the reception level stored in the beam memory 32 A and for storing the results of the calculation in the beam target memory 33 A is as follows: The central processor unit 28 reads those signals of the reflected waves , which corresponds to the five small areas arranged in the longitudinal direction (vertically) and which have been stored in the beam memory 32 A, extracts data from the read signals which exceed a threshold value. The extracted data are sequentially stored in the memory areas [BT0], [BT1], [BT2],. . . the beam target memory 33 A stored. In the example shown in FIG. 8, distances to and lateral positions of two reflectors R ₁ , R ₁ on / on a road and distances to and lateral positions of two reflectors R ₂ , R ₂ , which are located on rear sections of the vehicle bodies from two targets T. ₂ , T ₃ are provided, ie a total of four reflectors R ₂ , sequentially in the memory areas [BT0], [BT1], [BT2],. . . the beam target memory 33 A stored.

A procedure will now be described for adding the signals indicating the reception level in the small areas, which are stored in the beam memory 32 A, to each other and for storing the result of the addition in the adding memory 32 B by means of the adding area selector 34 . The detection of the respective target is carried out for each of the first to fifteenth detection areas K1 to K15. The detection of a target T in the first detection area K1 is described as an example. The first detection area K1 is formed by connecting / merging the first base area F1 with the second base area F2, and the adding memory 32 B contains memory areas for storing seventeen data points [D195, F1], [D196, F1],. . [D199, F2] and [D200, F2] corresponding to the first detection area K1 (see FIG. 5).

Fig. 6 shows a horizontal portion of the first to fifteenth detection range K1 to K15. In fact, the small areas contained in each of the detection areas K1 to K15 are arranged in five layers vertically overlapping each other, and consequently there are five small areas per beam in each detection area.

As can be seen from Fig. 7, for example, the data point [D200, F1] stored in the memory area of the distance address [200] in the first base area F1 includes a value obtained by adding signals of the twenty-five small areas indicative of the beam no. 1 to 5 correspond to, is / is delivered. The content of this data value is represented by

[D200, F1] = Σ (B1: B5) / 25.

This corresponds to an average obtained by adding the reception level signals from the distance of the distance address [200] in the twenty-five small areas that represent laser beams Nos. 1 through 5 and by dividing the resulting value by 25 is / will be delivered.  

In the same way, the data point [D199, F1] stored in the memory area of the distance address [199] in the first base area F1 is supplied by adding the reception level signals from the 20 small areas corresponding to beams Nos. 1 to 4 . The content of this data value is represented by

[D200, F1] = Σ (B1: B4) / 20.

This corresponds to an average obtained by adding the reception level indicating signals from the distance of the distance address [199] in the 20 small areas that correspond to rays Nos. 1 to 4 and through Dividing the resulting value by 20 is delivered.

In the same way, the data point [D200, F2] stored in the memory area of the distance address [200] in the second base area F2 is supplied by adding the signals indicating reception level from the twenty-five small areas corresponding to the beams Nos. 6 to 10. The content of this data value is represented by

[D200, F2] = Σ (B6: B10) / 25.

This corresponds to an average obtained by adding the reception level signals from the distance of the distance address [200] in the 25 small areas that correspond to rays Nos. 6 to 10 and through Dividing the resulting value by 25 is delivered.

The central processor unit 28 reads the data points [D195, F1], [D196, F1]. . . [D199, F2] and [D200, F2] stored in the 17 memory areas corresponding to the first and second base areas F1 and F2, and calculates 11 data points [D190, K1], [D191, K1], [D192, K1] . . . [D199, K1] and [D200, K1] in the first detection area K1 formed by connecting / merging the first and second base areas F1 and F2 based on this data.

As can be seen from Fig. 7, the five data points are [D190, K1], [D191, K1]. . . [D194, K1] in the first detection area K1, which are closer to the vehicle V, those in a section that does not contain the first base area F1 and only the second base area F2. The five data points [D199, K1], [D191, K1]. . . [D194, K1] are themselves five data points [D190, F2], [D191, F2]. . . [D194, F2] in the second base area F2.

On the other hand, the six data points are [D195, K1], [D196, K1]. . . [D200, K1] in the first detection area K1, which are further from the vehicle V, those in a section that includes both the first and the second Contains base area F1 and F2. Hence the six data points [D195, K1], [D196, K1]. . . [D200, K1] mean values obtained by adding the six Data points [D195, F1], [D196, F1]. . . [D200, F1] in the first base area F1 with the six data points [D195, F2], [D196, F2]. . . [D200, F2] in second base area F2 and by dividing the resultant Value delivered by 2 is / will be.

For example, the data point [D200, K1] of the distance address [200] in the first detection area K1 an average value which is obtained by adding the Data point [D200, F1] in the first base area F1 and the data point [D200, F2] in the second base area F2 with one another and by dividing of the resulting value is delivered by 2 and consequently is represented by [D200, K1] = ([D200, F1] + [200, F2]) / 2.

When calculating the eleven data points [D190, K1], [D191, K1]. . . [D200, K1] is finished in the first detection area K1 in the above manner, a peak value point (maximum) is extracted. When the eleven data points are given by
[D190, K1] = 20
[D191, K1] = 15
[D192, K1] = 42
[D193, K1] = 80 (peak value point)
[D194, K1] = 60
[D195, K1] = 37
[D196, K1] = 20
[D197, K1] = 30
[D198, K1] = 27
[D199, K1] = 16 and
[D200, K1] = 18,
the data point [D193, K1] exceeding a pre-set threshold (for example 70) is a peak value point. It is thus detected that a target T occurs at a point in the direction of the first detection area K1 at a distance from the vehicle V corresponding to the distance address [193] (96.5 m in front of the vehicle V).

The peak points are extracted in all detection areas K1 to K15, and the distances and lateral positions of the respective target in accordance with the peak points are stored in the plurality of storage areas in the destination memory 33 B.

Each of areas shown by reference numeral of three A _1, A ₂ and A ₃ in Fig. 6 is a group of regions corresponding to the extracted from the 32 B stored in the memory be added data peak points. The area indicated by reference number A ₁ is an area in which the reflector R ₁ , which has a higher reflectivity and is attached to the road, and the target T ₁ are detected in an integrally "fused" manner, and this area is represented by a group of three data points [D191, K1], [D191, K2] and [D191, K4] over the three detection areas K1, K2 and K4.

The area indicated by reference numeral A ₂ is an area in which the reflector R ₁ , which has a high reflectivity and is attached to the road, is detected, and this area is defined by a group of two data points [D198, K1] and [D198, K2] represented over the two detection areas K1 and K2. The area indicated by reference numeral A ₃ is an area in which the two targets T ₂ and T _{3 are} detected, which have the reflectors R _{2 of} high reflectivity at the rear portion of their vehicle bodies and drive side by side. This area is represented by a group of six data points [D197, K7], [D197, K8], [D197, K9], [D197, K11], [D197, K12] and [D197, K13] over the seven detection areas K7 up to K13.

If the highly reflective reflectors R ₁ and R ₂ on the road and the targets T ₁ ,. . . the following problem may occur. These reflectors R ₁ and R ₁ can be identified as a single object due to the integral "merging". Therefore, it is ensured according to the present invention that a distinction between the reflectors R ₁ and R ₁ and the targets T ₁ ,. . . can be performed, and the individual distances to these objects and the individual lateral positions of the same can be precisely detected in the following manner.

As shown in Fig. 6, the three data points [D191, K1], [D191, K2] and [D191, K4] have been stored in the destination memory 33 B for the indicated by the reference character A ₁ range. However, since the reflector R _{1 is present} on the road in the area indicated by the reference symbol A ₁ , the data corresponding to the reflector R _{1 were} stored in the beam target memory 33 A (see FIG. 8). Therefore, from the three data points [D191, K1], [D191, K2] and [D191, K4] in the deleted by the reference character _A1 in Fig. 6 is displayed, the region of the data value of a stored with the address of the beam target memory 33 A Data value for the reflector R _{1 has the} same address. More precisely: the data value for the reflector R ₁ stored in the beam target memory 33 A is present in the second base area F2, and the three data points [D191, K1], [D191, K2] and [D191, K4] stored in the target memory 33 B thus become the data points [D191, K1] and [D191, K2] containing the second base area F2 are deleted, and only the data point [D191, K4] remains in the target memory 33 B. The data value read out from the beam target memory 33 A becomes the reflector R ₁ then newly stored in the target memory 33 B.

As a result, the data is deleted in a whitened portion of the by reference characters A ₁ in Fig. 9 indicated range, and remain of the target T ₁ corresponding 33 B stored in the destination memory data point [D191, K4] and the reflector R ₁ on the road corresponding data value transferred from the beam target memory 33 A to the target memory 33 B. In this way, the target T ₁ and the reflector R ₁ on the road are correctly distinguished from one another.

In the area indicated by reference numeral A ₂ in Fig. 6, for the wave reflected by the reflector R ₁ on the road, the two data points [D198, K1] and [D198, K2] were stored in the target memory 33 B, and further the data value for the reflector R _{1 is} stored in the beam target memory 33 A (see FIG. 8). The data stored in the beam target memory 33 A for the reflector R ₁ are contained in the two data points [D198, K1] and [D198, K2], which are stored in the target memory 33 B, and consequently the two data points [D198, K1] and [D198, K2] are deleted from the target memory 33 B, and the data for the reflector R ₁ , which are stored in the beam target memory 33 A, are stored again in the target memory 33 B in their place.

As a result, the data in a white portion of the area indicated by reference numeral A ₂ in Fig. 9 is deleted, and only the data corresponding to the reflector R ₁ on the road and transferred from the beam target memory 33 A to the target memory 33 B remains. In this way, the lateral width of the reflector R ₁ on the road is precisely detected.

In the area indicated by the reference symbol A ₃ in FIG. 6, the six data points [D197, K7] for the reflected waves from the two targets T ₂ and T ₃ . . . [D197, K13] exclusively [D197, K10] stored in the target memory 33 B, and furthermore the data for the four reflectors R ₁ ,. . . stored in the beam target memory 33 A (see FIG. 8). These six data points contain all data for the four reflectors R ₂ ,. . ., which are stored in the beam target memory 33 A, and consequently the six data points are deleted from the target memory 33 B, and instead the data stored in the beam target memory 33 A for the four reflectors R ₂ ,. . . newly stored in the target memory 33 B.

As a result, the data in the whitened section of the deleted by the reference numeral _A3 in FIG. 9 display area, and there remain only by the beam target memory 33 A to the destination memory 33 B transferred, the four reflectors R _2,. . . corresponding data. In this way, the two targets T ₂ and T _{3 are} precisely distinguished from one another.

The operation described above and the detection method described above will be further described with reference to a flow chart shown in FIGS . 10 to 12.

First, in step S1, the emission of a laser beam to a small area and the reception of a reflected wave are carried out. In step S2, a signal indicating a reception level of the reflected received wave is AD-converted by an AD converter 29 for each pulse signal output by the base clock circuit 31 . In step S3, the data value supplied by the AD conversion is stored in a predetermined memory area in the beam memory 32A . For example, the data value stored in the beam memory 32 A in [D5] is a value resulting from the AD conversion of the signal indicating the reception level of the wave reflected from a target, which target is located at a position 2.5 m from the target Vehicle V occurs, and the data value stored in [D200] is a value resulting from the AD conversion of the signal indicating the reception level of the wave from a position 100.0 m from the vehicle V occurring target is reflected.

If data corresponding to a beam is stored in the beam memory 32 A in step S4, one of the data points stored in the beam memory 32 A which exceeds a preset threshold value is extracted as a peak point in step S6. In step S7, the counted number of basic clock pulses becomes. the distance to the target is calculated on the basis of the data corresponding to the peak point, and a lateral position of the target is calculated in step S8 from the radiation direction of the laser beam on the basis of the data corresponding to the peak point. When the extraction of all the peak points in the one beam is finished in step S9, the target distances and target side positions corresponding to the extracted peak points are stored in the data areas [BT0], [BT1], [BT2], in step S10. . . stored in the memory areas of the beam target memory 33 A. In step S11, the data stored in the ray memory 32 A data is distributed by the Addierbereichswähler 34 and added to each other and stored 32 B in the corresponding memory areas of the adding memory and the data memory in the beam are then deleted 32 A in step S12.

The procedure described above is carried out sequentially for ten beams contained in the first detection area K1 (see step S13). When all of the data in the first detection area K1 32 B stored in step S13 in the memory be added, the flow advances to step S14. In step S14, a preset threshold value the border data value is extracted as a peak point from the 32 B stored in the memory data be added. In step S15, a distance to the destination is calculated from the address in the adding memory 32 B in which the data value of the peak point was stored. In step S16, the side position of the target is calculated from the number of the detection area. In the next step S17, the flow of steps S14 to S16 is repeated until the extraction of all peak points of the data in the first detection area K1 is finished, and in step S18, the target distances and the target side positions corresponding to the extracted peak points are used as data [T0] , [T1], [T2],. . . stored in the memory areas of the target memory 33 B.

When the above procedures for all the detection areas of the first to 15th detection areas K1 to K15 are finished in the subsequent step S19, the flow proceeds to step S20. After the data (see FIG. 8) of 33 A stored in the beam target memory peak points are read out at step S20, in step S21 determines whether the data that was stored 33 B in the destination memory, read the addresses for the beam from the beam target memory 33 A Include data. If a corresponding data value stored in the target memory 33 B occurs, the corresponding data value is deleted from the target memory 33 B in step S22. The data of the peak points read out from the beam target memory 32 A are then re-stored in the target memory 33 B in step S23.

If in step S24 all the data in the beam target memory 33. A read out, the data (see Fig. 9) for the target intervals and target page positions 33 B are stored in the destination memory, in the next step S25, for example, to a driving control / regulating device or an automatic braking device and in step S26 the adding memory 32 B, the beam target memory 33 A and the target memory 33 B are deleted.

Even if, due to the presence of highly reflective objects, such as reflectors R ₁ and R _2, a plurality of targets may be detected in an integrally "fused" manner after the detection of the targets by adding together the signals indicative of the reception levels of the reflected waves, the targets can be detected precisely, preventing integral "merging" by performing the detection of the targets without adding the reception levels of the waves reflected by such highly reflective objects.

If no highly reflective object occurs, the target is detected by a result from the addition of the signals that the reception level in the display individual smaller areas, resulting value with the Threshold is compared. Even if the target is not a reflector has or was dirty / colored, the generation of a Detection errors can be avoided. Even if the laser beam is spread / distributed like a ray from the vehicle V in addition, the the reception level of which is essentially the reflected waves added together over the entire surface of the target are, without being influenced by the size of the distance to the target, because the lateral width of each of the detection areas K1 to K15 is always one constant value (1.6 m) regardless of the distance from vehicle V. is. This enables the target to be captured, resulting in a leads to remarkably increased comprehension. Because the majority of detection areas K1 to K15, the lateral width of 1.6 m (the is substantially equal to the side width of the vehicle V), are arranged so that they can overlap each other by 0.8 m furthermore, the entire target can be reliably detected regardless of the lateral position of the target, inevitably by one of the Detection areas K1 to K15 in an overlapping manner.

It now becomes a second embodiment of the present invention described.

In the above described first embodiment, it is determined whether the data that have been stored in the destination memory 33 B, which include the addresses of the read out of the target memory beam 33 A data. If a corresponding data value has been stored, the data value is deleted from the target memory 33 B, and the data value of the peak point read out from the beam target memory 33 A is stored again in the target memory 33 B. The distance to and the lateral position of the target stored in the target memory 33 B are used as the data for the target. Instead of this technique, however, a technique according to the second embodiment described below can be used.

As in the first embodiment, a peak point is first extracted from the data in the beam memory 32 A and a distance to a target is calculated from the targeted pulse number of pulses from the base clock based on the data of the peak point. Furthermore, a lateral position of the target is calculated from the direction of the laser beam emission based on the data of the peak point. When the extraction of all of the peak points for one beam is finished, the target distances and target side positions corresponding to the peak points are stored in the data areas [BT0], [BT1], [BT2],. . . stored in the memory areas of the beam target memory 33 A. The procedure up to this point is the same as that of the first embodiment (see steps S1 to S10).

Then, the data of the peak points corresponding to the data stored in the beam target memory 33 A are deleted from the beam memory 32 A, and the remaining data are distributed by the adding area selector 34 and added and stored in the corresponding storage areas of the adding memory 32 A. The data in the beam memory 32 A are then deleted. The above procedure is carried out sequentially for all rays contained in a detection area. At a time when all the data 32 B stored in this detection area be added memory, a preset threshold value border data is extracted as a peak point from the 32 B stored in the memory data be added. For example, the contemplated by the numeral _A1 in Fig. 6 range indicated below. After storage in the beam target memory 33 A, the data value corresponding to the highly reflecting reflector R ₁ which is attached to the road was deleted from the beam memory 32 A. The data value of the peak point extracted from the adding memory 32 B is therefore only the data value corresponding to the target T ₁ .

Subsequently, a distance to the target is calculated from the address in the adding memory 32 B in which the data value of the peak point was stored, and a side position of the target is calculated based on the number of the detection area (this corresponds to steps S11 to S16). At a time when the extraction of all the peak points in a detection area is finished, the target distances and target side positions corresponding to the extracted peak points are shown as data [T0], [T1], [T2],. . . stored in the memory areas of the target memory 33 B (this corresponds to steps S17 and S18). The above procedures are repeated sequentially to scan all of the detection areas (this corresponds to step S19).

Then, the target distances and target side positions, which are stored in the beam target memory 33 A, and the target distances and the target side positions, which are stored in the target memory 33 B, become a vehicle control device, for example a driving control device or an automatic braking device , is output, and thereafter the adding memories 32 B, the beam target memory 33 A and the target memory 33 B are deleted (this corresponds to steps S25 and S26; steps S20 to S24 are therefore not necessary).

Even according to the second embodiment, a function and Effect similar to that of the first embodiment is provided become.  

A third embodiment of an object detection device will now be described with reference to FIGS. 13 to 16.

As can be seen by comparing the first embodiment shown in Figs. 1 and 2 with the third embodiment shown in Figs. 13 and 14, the object detection apparatus according to the third embodiment of the present invention includes a transmission and reception beam scanning section 4 'which is provided instead of the receiving beam scanning section 4 of the object detection device according to the first embodiment. The "scanning section" 4 'can also be referred to as a scanning or searching section 4 ' (or - in any case in the case of the exemplary embodiment described here - also as a sweeping or swiveling section 4 ').

The transmission and reception beam scanning section 4 'includes a beam transmission and reception mirror 20 ', a motor 22 'for rotating the beam transmission and reception mirror 20 ' about a transverse axis 21 ', and a motor drive circuit 23 ' for controlling the drive of the engine 22 '. A laser beam reflected by the beam transmission mirror 13 is again reflected by the beam transmission and reception mirror 20 ', and the target T is scanned laterally and vertically by the point-like laser beam, which is limited in its vertical and lateral width.

As shown in Figs. 15 and 16, the period of lateral scanning (scanning) with the laser beam by the reciprocating rotation of the beam transmitting mirror (reference numeral 13 ) is 200 msec, and the period of vertical scanning (scanning) with that Laser beam due to the reciprocating rotary movement of the beam transmitting and receiving mirror 20 'is 2.5 msec. By vertically swiveling back and forth or scanning the beam receiving area by means of the reciprocating rotary movement of the beam transmitting and receiving mirror 20 ', the vertical scanning period of the beam receiving area is also 2.5 msec.

This is the same value as the value for the period of the vertical Scanning with the laser beam.

As in the first embodiment, the entire range includes Capture the target a total of 400 small areas by dividing the entire area vertically into five sections and side dividing the total area into 80 Sections is formed. The 400 small areas are zigzag Way sampled in 200 msec. Even according to the third embodiment can have a function and an effect similar to that of the first off leadership can be achieved.

The object detection device according to each of the embodiments uses a laser, but other electromagnetic waves, like millimeter waves, can be used instead of laser radiation. Further is the number of small areas that cover the total area of the target, not to 400 as in the disclosed embodiments limited. There are also no restrictions on the detectable target T. In addition to a vehicle in front, each Object can be detected on a street. It also expressly points out noted that in relation to the invention Object detection device and the inventive Object detection procedure on the revelation of the German Patent application P 199 32 975 can be used in addition.

Although embodiments of the present invention are described , it is understood that the present invention is not limited to the above described embodiments is limited, and that varied Modifications in the design or layout are provided can, without the spirit and scope of the invention, as in the Defined claims to deviate.  

If a vehicle in front of another vehicle and a reflector On a street side by side, signals are given that Specify the reception level of waves reflected by the objects for adding each beam together to perform target acquisition. Since the wave reflected by the reflector has a high intensity, it happens that the vehicle in front and the reflector in one integrally fused shape can be detected. In one by that of that Reflected wave affected area is therefore only the The reflector detects the reception level of the reflected waves without addition indicating signals for each beam. In an area characterized by that of the reflector reflected wave is not affected, it will preceding vehicle detected by adding together the signals of the reflected waves. So the reflector and the one ahead can Vehicle detected and distinguished from each other.

Claims (13)

1. Object detection device for detecting an object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) in an object detection area by emitting an electromagnetic wave and receiving one from the reflection of the electromagnetic wave by the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) resulting reflected wave, comprising transmitting and receiving means ( 1 , 2 , 3 , 4 ) for emitting the electromagnetic wave and receiving the reflected wave for each of a plurality of small areas into which the object detection area a first storage means ( 33 A) for storing signals indicating reception levels of waves reflected from the small areas in accordance with the time delay from transmission to reception of the waves, a second storage means ( 33 B) for storing Signals that indicate reception levels of waves reflected in a plurality of detection areas (K1,..., K15) in the form of in accordance in accordance with the time delay from the transmission to the reception of the waves, the reception signals added together, the detection ranges (K1,. . . K15) are defined by grouping adjacent ones of the plurality of small areas such that they have a predetermined page width, and an object detection means ( 25 ) for detecting a distance to the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) Basis of the result of a comparison of an output from the first storage means ( 33 A) with an output from the second storage means ( 33 B). 2. Object detection device according to claim 1, characterized in that the second storage means ( 33 B) a side position of the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) on the basis of a side position of the detection area (K1;... K15) in which the object was recorded. 3. Object detection device according to claim 1 or 2, characterized characterized in that the plurality of detection areas (K1,..., K15) are / are defined in such a way that they are mutually related to each other Overlap half of their lateral width. 4. Object detection device according to one of claims 1 to 3, characterized in that the second storage means ( 33 B) extracts and outputs at least one of the values exceeding a threshold value, which results from the addition of a plurality of signals which indicate reception levels in accordance with the Time delay from the transmission to the reception of the electromagnetic wave result. 5. Object detection device according to one of claims 1 to 4, characterized in that the transmitting and receiving means ( 1 , 2 , 3 , 4 ) sequentially emits the electromagnetic wave in the lateral direction, and that the first storage means ( 33 A) the lateral position of the Object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) is detected based on the timing of the emission of the electromagnetic wave to each of the small areas. 6. Object detection device according to one of claims 1 to 5, characterized in that the object detection device is attached to a vehicle (V) to the object occurring in front of the vehicle in the direction of movement of the vehicle (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) to be detected, the lateral width of the detection area being set based on the lateral width of the vehicle V. 7. Object detection device according to claim 6, characterized indicates that the lateral width of the detection area (K1;...; K15) is set to be substantially equal to that lateral width of the vehicle (V). 8. Object detection device according to one of claims 1 to 5, characterized in that the object detection device is attached to a vehicle (V) to the object occurring in front of the vehicle in the direction of movement of the vehicle (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) to detect occurring vehicle, the lateral width of the detection area (K1;...; K15) is set based on the width of a road lane. 9. Object detection device according to claim 8, characterized characterized in that the lateral width of the detection area (K1;...; K15) is set so that it is substantially equal to the Lane width is. 10. Object detection device according to one of claims 1 to 9, characterized in that the object detection means ( 25 ) detects the distance to and the side position of the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) based on data, they remain after deleting the data for the object distances and the object page positions on the basis of the data stored in the first storage means ( 33 A) from the data for the object distances and the object page positions on the basis of the data stored in the second storage means ( 33 B), and on the basis of the data stored in the first storage means ( 33 A). 11. Object detection device according to one of claims 1 to 10, characterized by a third storage means ( 33 A) for storing data for object distances and object page positions on the basis of the data stored in the first storage means ( 33 A) and by a fourth storage means ( 33 B) for Storage of data for object distances and object side positions on the basis of the data stored in the second storage means ( 33 B), the object detection means ( 25 ) being the distance to and the side position of the respective object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) based on data that remains after deleting the data for the object distances and the object page positions, which are stored in the third storage means ( 33 A), from the data for the object distances and the object page positions, which are stored in the fourth storage means ( 33 B) and on the basis of the data stored in the third storage means ( 33 A). 12. Object detection device according to one of claims 1 to 9, characterized by a third storage means ( 33 A) for storing data for object distances and object page positions on the basis of the data stored in the first storage means ( 33 A) and by a fourth storage means ( 33 B) Storing data for object distances to and object side positions on the basis of the data stored in the second storage means ( 33 B), the second storage means ( 33 B) storing data which remain after deletion of data containing the data stored in the third storage means ( 33 A) correspond from the data stored in the first storage means ( 33 A), and wherein the object detection means ( 25 ) detects the distance to and the lateral positions of the respective object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) based on the data for the object distances and the object page positions stored in the fourth storage means ( 33 B) and on the basis the data stored in the third storage means ( 33 A). 13. Object detection method for detecting an object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) in an object detection area by emitting an electromagnetic wave and receiving one from the reflection of the electromagnetic wave by the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) resulting reflected wave, comprising:

• Emitting the electromagnetic wave and receiving the reflected wave for each of a plurality of small areas into which the object detection area is divided,
• Providing first data representing reception levels of waves reflected from the small areas in accordance with the time delay from transmission to reception of the waves,
• Providing second data representing reception levels of waves reflected in a plurality of detection areas (K1,..., K15) in the form of reception signals added together in accordance with the time delay from transmission to reception of the waves, the detection areas ( K1,... K15) are defined by grouping adjacent ones of the plurality of small areas so as to have a predetermined page width, and
• - Detecting a distance to the object (T ₁ ; T ₂ ; T ₃ ; R ₁ ; R ₂ ) on the basis of a result of the comparison of the first and the second data.